1. Field of the Invention
This present invention relates to a method and apparatus for recovering residual tar or oil from a fluid medium. It is particularly, though not exclusively, concerned with the recovery of the residual material comprising the heavier components of crude oil from oil spillages in the sea.
When crude oil is accidentally spilled into the sea, for example by leakage from off-shore oil platforms or from oil tankers, the lighter, more volatile constituents of the crude oil evaporate, leaving the heavier constituents floating on the water surface as a thick sticky mixture presenting a severe problem of pollution. As the frequency and scale of such accidental spillages increases, ever increasing attention is being directed to tackling the problems of pollution of the sea and beaches.
The rate at which the lighter constituents evaporate depend upon the water and air temperature, and in geographical areas, such as the Arabian Gulf, where these temperatures are relatively high, the spilled oil relatively quickly takes the form of a sticky mat comprising the heavier oil constituents; this mat is, effectively, tar. Depending upon the size of the spillage and the sea conditions, the mat may break up into relatively small pieces, known as tar balls.
2. Description of the Prior Art
Existing techniques for recovery of the tar have not been entirely successful. One major problem area is in the handling of the tar once it has been removed, by whatever means, from the sea. It is known, for example, to use skimmers of oleophilic material to which the spilled oil clings, the oil subsequently being squeezed or scraped from the skimmers. The devices for removing the oil from the skimmers tend to become clogged, and therefore require constant attention.